Many conventional oil wells are operated by a downhole pump at or close to the bottom of the well, the pump being of a conventional reciprocating kind actuated by a rod string which in turn is reciprocated vertically by a pump jack. Recently, many conventional reciprocating pumps have been replaced by rotary-drive progressive cavity pumps. The rotary pumps are particularly suited for the production of crude oil laden with sand and water.
In the conventional vertically reciprocating pumps, the apparatus is typically constructed in such a way that a single stuffing box provides control of leakage and loss of oil. This conventional stuffing box is stationary and is secured to a stationary housing. The part of the upper portion of the rod which actually contacts the stuffing is usually highly polished, thus ensuring minimal leakage and minimal damage to the pacing material. With the introduction of rotary pumps, it has been generally found that, if the conventional stuffing box (developed for vertical pumps) is used for the rotary pumps, oil leakage develops relatively early, requiring frequent maintenance and frequent replacement of the packing material.
Prior Art
The following provide a general survey of the background art:
U.S. Pat. No. 2,471,198, issued on May 24, 1949 to D. R. Cormany; PA0 U.S. Pat. No. 3,891,031, issued on Jun. 24, 1975 to Ortiz; PA0 U.S. Pat. No. 4,087,211, issued on May 2, 1978 to Pochyly; PA0 U.S. Pat. No. 4,089,624, issued on May 16, 1978 to Nichols et al; PA0 U.S. Pat. No. 4,314,611, issued on Feb. 9, 1982 to Willis; PA0 U.S. Pat. No. 4,372,379, issued on Feb. 8, 1983 to Kulhanek et al.